1. Field of the Invention
The present invention relates to novel 4-anilino[2,3-b]quinoline derivatives, which are found to have the ability to inhibit the growth of a variety of tumor/cancer cells, especially leukemia, colon, melanoma, and breast cancer cells, and the preparation processes of these derivatives, and their uses in the manufacture of pharmaceutical compositions.
2. Description of the Related Art
Acridine derivatives, especially 9-anilinoacridines, have been extensively studied as potential chemotherapeutic agents due to their capability of intercalating DNA leading to the inhibition of mammalian topoisomerase II (Atwell, G. J. et. al., J. Med. Chem. 1972, 15, 611-615; Denny, W. A. et. al., J. Med. Chem. 1978, 21, 5-10; Denny, W. A. et. al., J. Med. Chem. 1982, 25, 276-315; Gamage, S. A. et. al., J. Med. Chem. 1994, 37, 1486-1494; Gamage, S. A. et. al., J. Med. Chem. 1997, 40, 2634-2642). 4xe2x80x2-(9-acridinylamino)methanesulfonyl-m-anisidine (amsacrine, m-AMSA) is reported to be specifically relevant and has become a useful clinical drug for the treatment of leukemia and lymphoma (Atwell, G. J. et. al., J. Med. Chem. 1972, 15, 611-615).
A tremendous amount of effort has been directed toward the design and preparation of new amsacrine analogues with the aim of developing new drug candidates with an improved broad spectrum of antitumor activity (Baguley, B. C. et. al., J. Med. Chem. 1981, 24, 520-525; Rewcastle, G. W. et. al., J. Med. Chem. 1986, 29, 472-477; Denny, W. A. et. al., J Med. Chem. 1987, 30, 658-663; Su, T. L. et. al., J. Med. Chem. 1995, 38, 3226; Stanslas, J. et. al., J. Med. Chem. 2000, 43, 1563-1572).
For example. 3-(acridin-9-ylamino)-5-(hydroxymethyl) aniline (AHMA) was reported to be superior to m-AMSA against the growth of certain solid tumors, such as mammary adenocarcinoma, melanoma, and Lewis lung carcinoma in mice. Unlike m-AMSA, AHMA, which has a 3,5-disubstituted anilino moiety, was resistant to the oxidative metabolism and, therefore, was expected to have longer half-life in plasma. (T. L. Su, T. C Chou, J. Y. Kim, J. T. Huang, G. Ciszewska, W. Y. Ren, G. M. Otter, F. M. Sirotnak, K. A. Watanabe, J. Med. Chem. 1995, 38, 3226). 
However, the above-mentioned studies focused only on the 9-anilinoacridine skeleton, with a wide variety of substituents on anilino- and/or acridine chromophore. No attempt has been carried out concerning the replacement of acridine with its isosteric furo[2,3-b]quinoline ring which constitutes an important group of bioactive natural products, such as dictamnine, robustine, and haplopine (Chen, I. S. et. al., Phytochemistry 1994, 36, 237-239; Zhao, W. et. al., Phytochemistry 1998, 47, 7-11).
Therefore, in the first aspect of this invention, the present invention provides novel 4-anilino[2,3-b]quinoline derivatives of formula (I): 
wherein
Y represents: S, O or NH
R1 represents a group selected from the group consisting of: 
xe2x80x83wherein
R4 represents: H or 
xe2x80x83wherein X represents O, S, NH or NOR, R in NOR being H or a C1-C4 alkyl group, and R6 represents H or a C1-C4 alkyl group;
R5 is selected from the group consisting of H, 
xe2x80x83and 
wherein X represents O, S, NH or NOR, R in NOR being H or a C1-C4 alkyl group, and R6 represents H or a C1-C4 alkyl group;
with the proviso that one of R4 and R5 is H;
R2 represents: H, halogen, a C1-C4 alkyl group, hydroxyl, a C1-C4 alkoxy group, nitro or amino; and
R3 represents: H, halogen, a C1-C4 alkyl group, hydroxyl, a C1-C4 alkoxy group, nitro or amino.
In the second aspect, the present invention provides a pharmaceutical composition which comprises the above-described derivative, in its free type or a pharmaceutically acceptable salt thereof, as an active ingredient in inhibiting the growth of tumor/cancer cells, especially leukemia, colon, melanoma, and breast cancer cells.
In the third aspect, the present invention provides processes for preparing the above-described derivatives of formula (I), as well as their intermediate compounds.
In particular, the present invention provides processes for preparing a compound of formula (Ixe2x80x2) 
wherein
Y represents: S, O or NH;
R1 represents a group selected from the group consisting of: 
xe2x80x83wherein one of R4xe2x80x2 and R5xe2x80x2 is H, and the other is 
xe2x80x83wherein R6 represents H or a C1-C4 alkyl group;
R2 represents: H, halogen, a C1-C4 alkyl group, hydroxyl, a C1-C4 alkoxy group, nitro or amino; and
R3 represents: H, halogen, a C1-C4 alkyl group, hydroxyl, a C1-C4 alkoxy group, nitro or amino;
the process comprising the step of reacting a compound of formula (A): 
xe2x80x83wherein
R2, R3 and Y are the same as those defined for formula (Ixe2x80x2); and
Xxe2x80x2 represents Cl, Br or I;
with a compound selected from the group consisting of a compound of formula 
xe2x80x83and a compound of formula 
xe2x80x83wherein R4xe2x80x2 and R5xe2x80x2 are the same as those defined for formula (Ixe2x80x2).
The above and other objects, features and advantages of the present invention will become apparent with reference to the following detailed description of the preferred examples.
The applicant noted that furo[2,3-b]quinoline system possesses a higher electron density than that of acridine systems and, therefore, is advantageous, since the major route of breakdown for m-AMSA in vivo is a non-enzymatically mediated attack of thiol at C(9), which would eventually result in loss of the side chain and the formation of inactive products (B. F. Cain, W. R. Wilson, B. C. Baguley, Mol. Pharmacol. 1976, 12, 1027; W. R. Wilson, B. F. Cain, B. C. Baguley, Chem.-Biol. Interact., 977, 18, 163; and R. L. Cysyk, D. Shoemaker, R. H. Adarnson, Drug Metab. Dispos. 1977, 5, 579).
In earlier researches, the applicant synthesized certain xcex1-methylindene-xcex3-butyrolactone-bearing quinolones and evaluated their cytotoxicities on the ground that, through the intercalation of quinolone, the xcex1-methylidene-xcex3-butyrolactone can specifically alkylate DNA molecule (K. C. Fang, Y. L. Chen, J. Y. Sheu, T. C. Wang, C C. Tzeng, J. Med. Chem. 2000, 43, 3809; C. C. Tzeng, K. H. Lee, T. C. Wang, C. H. Han, Y. L. Chen, Pharmaceut. Res. 2000. 17, 715; and S. L. Hsu, Y. L. Chen, K. C. Fang, J. Y. Sheu, C. C. Tzeng, Helv. Chim. Acta 2001, 84, 874). This versatile xcex1-methylidene-xcex3-butyrolactone moiety is appended on the 9-anilino group (see compound 6 shown in the following synthesis scheme I) in an attempt to prepare a bifunctional compound in which the furo[2,3-b]quinoline moiety acts as an intercalator while the lactone ring plays the role of an alkylating unit.
Based on the above, the applicant further developed new bioisosteric isomers of AHMA, i.e. compounds of formula (I) or pharmaceutically acceptable salts thereof: 
wherein
Y represents: S, O or NH;
R1 represents a group selected from the group consisting of: 
wherein
R4 represents: H or 
wherein X represents O, S, NH or NOR, R in NOR being H or a C1-C4 alkyl group, and R6 represents H or a C1-C4 alkyl group;
R5 is selected from the group consisting of H, 
and 
wherein X represents O, S, NH or NOR, R in NOR being H or a C1-C4 alkyl group, and R6 represents H or a C1-C4 alkyl group;
with the proviso that one of R4 and R5 is H;
R2 represents: H, halogen, a C1-C4 alkyl group, hydroxyl, a C1-C4 alkoxy group, nitro or amino; and
R3 represents: H, halogen, a C1-C4 alkyl group, hydroxyl, a C1-C4 alkoxy group, nitro or amino.
Preferably, Y is O.
Preferably, R2 is H.
Preferably, R3 is H.
Preferably, R1 is selected from the group consisting of 
In a preferred embodiment, R1 is 
wherein R is H or methyl.
In another preferred embodiment, R1 is 
wherein R is H or methyl.
Specifically, the applicant synthesized certain mono-substituted 4-anilinofuro[2,3-b]quinoline derivatives, in which the anilino moiety thereof is substituted, at either the C(3xe2x80x2) or C(4xe2x80x2) position, with an Ac group as well as its corresponding oxime and methyloxime. It is expected that these substituents would form H-bonding with a DNA molecule during the intercalation process of the tricyclic furo[2,3-b]quinoline moiety with the DNA molecule.
The compounds of formula (I) according to this invention have been found to exhibit inhibitory activities against the growth of a variety of tumor/cancer cells, especially leukemia, colon, melanoma, and breast cancer cells. Therefore, the present invention also envisions the application of the compounds of formula (I) of this invention in the manufacture of pharmaceutical compositions.
According to this invention, there is provided a pharmaceutical composition comprising a therapeutically effective amount of the 4-anilino[2,3-b]quinoline derivatives described above, or a pharmaceutically acceptable salt thereof.
As used herein, the pharmaceutically acceptable salts include salts with inorganic acids, such as hydrochloride, hydrobromide, sulfate and phosphate; those with organic acids, such as acetate, maleate, tartrate, methanesulfonate; and those with amino acids, such as arginine, aspartic acid and glutamic acid.
The compounds of the present invention may also be present as a hydrate or as a stereoisomer. Therefore, it is contemplated that these hydrates and stereoisomers fall within the technical concept of the present invention.
Optionally, the pharmaceutical composition according to this invention may additionally comprise a pharmaceutically acceptable carrier widely employed in the art for the manufacture of medicaments. For example, the pharmaceutically acceptable carrier can include one or more than one of the following reagents: solvents, disintegrating agents, binders, excipients, lubricants, absorption delaying agents and the like.
The pharmaceutical composition according to this invention may be administered parenterally or orally in a suitable pharmaceutical form. Suitable pharmaceutical forms include sterile aqueous solutions or dispersions, sterile powders, tablets, troches, pills, capsules, and the like.
In addition, the active compounds of the present invention may be incorporated into sustained-release preparations and formulations. Optionally, the pharmaceutical composition according to this invention may be administered alone or in conjunction with an additional anticancer agent, such as such as Mitomycin, Adriamycin, Actinomycin, cis-platin and the like.
The new compounds of formula (I) may be prepared according to the following reaction schemes and protocols.
According to this invention, there is provided a method for producing a compound of formula (Ixe2x80x2): 
wherein
Y represents: S O or NH;
R1xe2x80x2 represents a group selected from the group consisting of: 
xe2x80x83wherein one of R4xe2x80x2 and R5xe2x80x2 is H, and the other is 
wherein R6 represents H or a C1-C4 alkyl group;
R2 represents: H, halogen, a C1-C4 alkyl group, hydroxyl, a C1-C4 
alkoxy group, nitro or amino; and
R3 represents: H, halogen, a C1-C4 alkyl group, hydroxyl, a C1-C4 alkoxy group, nitro or amino;
the process comprising the step of reacting a compound of formula (A): 
xe2x80x83wherein
R2, R3 and Y are the same as those defined for formula (Ixe2x80x2); and
Xxe2x80x2 represents Cl, Br or I; with a compound selected from the group consisting of a compound of formula 
xe2x80x83and a compound of formula 
xe2x80x83wherein R4xe2x80x2 and R5xe2x80x2 are the same as those defined for formula (Ixe2x80x2). In a preferred embodiment, the used compound of formula (A) is reacted with a compound of formula 
In a further preferred embodiment, the compound of formula (A) is reacted with the compound of formula 
preferably 
(p-aminoacetophenone) or 
(m-aminoacetophenone). These aminoacetophenones may be chemically modified according to the prior methods, such as the method disclosed in Doud, et al. J Am. Chem. Soc. 1958, 80, 2205-2210, so that the methyl group present thereon is replaced by a larger alkyl group (e.g. a C2-C4 alkyl group).
Optionally, when the compound of formula 
is used, the resultant compound of formula (Ixe2x80x2) may be further treated with a compound of formula NH2OR, wherein R is H or a C1-C4 alkyl group, such that the 
group in the 
group of said compound of formula (Ixe2x80x2) is chemically modified to a 
group.
The compound of formula NH2OR may be prepared, e.g. according to the following prior method: 
(Kim, J. N. et al., Synth. Commun., 1992, 22, 1427-1432).
Alternatively, the resultant compound of formula (Ixe2x80x2) may be treated with hydroxylamine, such that the 
group in the 
group of said compound of formula (Ixe2x80x2) is chemically modified to a 
group, followed by treating the thus chemically modified compound of formula (Ixe2x80x2) with a C1-C4 alkyl halide, such that the 
group is chemically modified to a 
group, wherein R6 is a C1-C4 alkyl group.
In a preferred embodiment of this invention, the compound of formula 
is a compound in which R4xe2x80x2 is H and R5xe2x80x2 is 
and the resultant compound of formula (Ixe2x80x2) is further treated with a compound of formula NH2OR, wherein R is H or a C1-C4 alkyl group, such that the 
group in said compound of formula (Ixe2x80x2) is chemically modified to a 
group.
In a preferred embodiment of this invention, the compound of formula 
is a compound in which R4xe2x80x2 is H and R5xe2x80x2 is 
and the resultant compound of formula (Ixe2x80x2) is further treated with ethyl 2-(bromomethyl)acrylate, such that the 
group in said compound of formula (Ixe2x80x2) is chemically modified to 
Optionally, when the compound of formula 
is used, the resultant compound of formula (Ixe2x80x2) may be further treated with a Lawesson""s reagent or P2S5, such that the 
group in the 
group of said compound of formula (Ixe2x80x2) is chemically modified to a 
group.
The Lawesson""s reagent is a commercial product available from Robinson Brothers Limited, and its chemical name is 4-methoxyphenylthiophosphine and has the following structural formula: 
The Lawesson""s reagent may be used according to the manufacturer""s recommendations as posted on the internet website.
Optionally, when the compound of formula 
is used, the resultant compound of formula (Ixe2x80x2) may be further treated with benzyldimethylphosphinimide, such that the 
group in the 
group of said compound of formula (Ixe2x80x2) is chemically modified to a 
group.
Concerning the use of benzyldimethylphosphinimide in the above chemical modification, reference is made to Wannagat, U.; Muenstedt, R. Phosphorus Sulfur, 1987, 29, 233-238.
In a preferred embodiment of the present process, the compound of formula (A) is 
The compound of formula 
may be produced by a process comprising the steps of:
(a) forming a compound of formula 
xe2x80x83from the reaction of a compound of formula 
xe2x80x83with HBr; and
(b) reacting the resultant compound 
xe2x80x83from step (a) with POCl3.
As an alternative, the above step (b) may be carried out using POCl3 and PCI5, or using SOCl2 in the presence of DMF.
In a further preferred embodiment of the present process, the compound of formula (A) is 
and the resultant compound of formula (Ixe2x80x2) may be further subjected to a hydrogenation reaction in the presence of Pd/C in CH2Cl2 to thereby form a compound of formula 
As an alternative, the above hydrogenation reaction may be carried out in the presence of NaBH4, LiAIH4 or Raney Ni.
The compound of formula 
may be formed from the reaction of a compound of formula 
and POCI3 (or POCl3 and PCl5, or SOCl2 in the presence of DMF).
For example, when the compound of formula 
is used as the starting material, the present compound of formula (Ixe2x80x2) or (I) may be produced according to the following synthesis scheme I: 
When the compound of formula 
is used as the starting material, the present compound of formula (Ixe2x80x2) or (I) may be produced according to the following synthesis scheme II: 
Reaction of the known substituted 2,3,4,9-tetrahydrofuro[2,3-b]quinolin-3,4-diones (compound 11) (Kuo, S. C. et. al., J Heterocyclic Chem., 1991, 28, 955) with POCl3 and H2O (30:1) yielded the respective 3,4-dichlorofuro[2,3-b]quinolines (compound 12) which was treated with 4-aminoacetophenone in EtOH to obtain 1-[4-(3-chlorofuro[2,3-b]quinolin-4-ylamino)phenyl]ethanone (compound 13). Hydrogenation of compound 13 in the presence of Pd/C resulted in 1-[4-(furo[2,3-b]quinolin-4-ylamino)phenyl]ethanone (compound 14, corresponding to compound 5 and compound 7 in scheme I).